@mdn/yari
v2.65.1
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![Testing](https://github.com/mdn/yari/workflows/Testing%20Yari/badge.svg) ![Prod Build](https://github.com/mdn/yari/workflows/Prod%20Build/badge.svg)
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Yari
Quickstart
Development on yari
involves updating the machinery that renders MDN content
or improving the structure and styling of the MDN UI (e.g. the styling of the
header). If you are more interested in contributing to the MDN content, you
should check out the content repo README
instead.
Before you can start working with Yari, you need to:
Fork the MDN content and yari repositories using the Fork button on GitHub.
Clone the forked repositories to your computer using the following commands (replace
[your account]
with the account you forked the repositories to):git clone https://github.com/[your_account]/content.git git clone https://github.com/[your_account]/yari.git
To run Yari locally, you'll first need to install its dependencies and build the app locally. Do this like so:
cd yari
yarn install
See the troubleshooting section below if you run into problems.
Now copy the .env-dist
file to .env
:
cp .env-dist .env
If you followed the instructions above and cloned the content
repo as a
sibling of your yari
repo, the CONTENT_ROOT
environment variable is already
set and Yari will be able to find the content it needs to render.
At this point, you can get started. Run the following lines to compile required files, start the Yari web server running, and open it in your browser:
yarn dev
open http://localhost:3000
If you prefer you can use yarn start
, which will re-use any previously
compiled files; this is "riskier" but faster. yarn dev
always ensures that
everything is up-to-date.
The yarn start
command also starts a server with slightly different behavior —
it doesn't automatically reload when its source code files change, so use with
caution.
See also our reviewing guide for information on how to review Yari changes.
Pull request requirements
Firstly, thank you for your interest in contributing to Yari! We do have a few requirements when it comes to pull requests:
- Please make use of a feature branch workflow.
- We prefer if you use the conventional commits format when making pull requests.
- Lastly, we require that all commits are signed. Please see the documentation about signed commits and how to sign yours on GitHub.
Thank you for your understanding! We look forward to your contributions.
How to stay up-to-date
Periodically, the code and the content changes. Make sure you stay up-to-date
with something along the following lines (replace yari-origin
with whatever
you called the remote location of the
original yari repo):
git pull yari-origin main
yarn
yarn dev
When you embark on making a change, do it on a new branch, for example
git checkout -b my-new-branch
.
License
All source code is MPL-2.0.
For content, see its license in the mdn/content repository.
Supported Platforms
yari
runs on Linux in CI, and when building for Production.
We also support Windows and MacOS, however we don't aim to proactively catch issues with CI on those platforms. If bugs arise, we welcome issues being filed, or PRs being opened to fix them.
How it works
Yari does a number of things, the most important of which is to render and serve
the MDN content found in the content repo.
Each document is stored as an index.md
(recommended) or index.html
file that
contains metadata presented as YAML
front-matter followed by
the document source.
The builder converts these "source files" into "build files" using a CLI tool that iterates over the files, builds the HTML, and lastly packages it up with the front-end code, ready to be served as static files.
Development
The yarn start
command encapsulates the front-end dev server (on
http://localhost:3000) and the server
(on http://localhost:5042).
All the sub-commands of yarn start
can be broken down and run individually if
you want to work more rapidly.
Setting up $EDITOR
If you configure an environment variable called EDITOR
, either on your system
as a whole or in the root .env
file, it can be used in the development server
to link to sources which, when clicked, open in your preferred editor/IDE. For
example, in the root of the repo you could run:
echo 'EDITOR=code' >> .env
Now clicking certain links will open files directly in the currently open VS
Code IDE (replace code
in the above command with a different text editor name
if needed, e.g. atom
or whatever). To test it, view any document on
http://localhost:3000 and click the "Open in your editor" button.
How the server works
The server
has two main jobs:
- Simulate serving the site (e.g. from a server, S3 or a CDN).
- Trigger builds of documents that haven't been built, by URL.
Linting
All JavaScript and TypeScript code needs to be formatted with prettier
and
it's easy to test this with:
yarn prettier-check
And conveniently, if you're not even interested in what the flaws were, run:
yarn prettier-format
When you ran yarn
for the first time (yarn
is an alias for yarn install
)
it automatically sets up a git
pre-commit hook that uses lint-staged
— a
wrapper for prettier
that checks only the files in the git commit.
If you have doubts about formatting, submit your pull request anyway. If you have formatting flaws, the pull request checks should catch it.
Upgrading Packages
We maintain the dependencies using Dependabot
in GitHub but if you want to
manually upgrade them you can use:
yarn upgrade-interactive --latest
Building
The server
builds content automatically (on-the-fly) when you're viewing
pages, but you can pre-emptively build all the content in advance if desired.
One potential advantage is that you can get a more complete list of all possible
"flaws" across all documents before you even visit them.
The most fundamental CLI command is:
yarn build
What gets built
Every index.html
becomes two files:
index.html
— a fully formed and complete HTML fileindex.json
— the state information React needs to build the page in the client
Flaw checks
When building you can enable specific "flaw checks" and their level of handling. Some flaws are "cosmetic" and some are more severe but they should never block a full build.
More information about how to set flaws can be found in docs/envvars.md
.
Essentially, the default is to warn about any flaw and you can see those flaws when using http://localhost:3000. For completed builds, all flaws are ignored. This makes the build faster and there's also no good place to display the flaws in a production-grade build.
In the future, we might make the default flaw level error
instead. That
means that any new edits to (or creation of) any document will break in
continuous integration if there's a single flaw and the onus will be on you to
fix it.
Icons and logos
The various formats and sizes of the favicon are generated from the file
mdn-web-docs.svg
in the repository root. This file is then converted to
favicons using realfavicongenerator.net. To
generate new favicons, edit or replace the mdn-web-docs.svg
file and then
re-upload that to realfavicongenerator.net.
Contact
If you want to talk to us, ask questions, and find out more, join the discussion on the MDN Web Docs chat room on Matrix.
Troubleshooting
Some common issues and how to resolve them.
Error: ENOSPC: System limit for number of file watchers reached
There are two options to resolve this.
Disable the watcher via
REACT_APP_NO_WATCHER
echo REACT_APP_NO_WATCHER=true >> .env
Increase
max_user_watches
:
See https://github.com/guard/listen#increasing-the-amount-of-inotify-watchers
Error: Cannot find module 'levenary'
We can't know for sure what's causing this error but speculate a bug in how
yarn
fails to resolve if certain @babel
helper libs should install its own
sub-dependencies. A sure way to solve it is to run:
rm -fr node_modules
yarn install
Error: listen EADDRINUSE: address already in use :::5042
The default server port :5042
might be in use by another process. To resolve
this, you can pick any unused port (e.g., 6000) and run the following:
echo SERVER_PORT=6000 >> .env
Yarn install errors
If you get errors while installing dependencies via yarn on a Mac, you may need to install some additional packages. Check the error message for the package name causing the problem.
First, install brew if you haven’t already
To fix problems with
gifsicle
:brew install automake autoconf libtool
To fix problems with
pngquant-bin
:brew install pkg-config
To fix problems with
mozjpeg
:brew install libpng sudo ln -s /opt/homebrew/Cellar/libpng/1.6.40/lib/libpng16.a /usr/local/lib/libpng16.a
You may need to adjust the path to libpng16.a
depending on the version of
libpng
you have installed.